The present invention relates to hermetic compressors and, more particularly, to a suction system for a hermetic compressor.
Hermetic compressors are utilized for circulating a refrigerant gas through a closed refrigerant system. In operation, the refrigerant vapor is fed into the interior of the compressor through an intake pipe in the sealed housing defining the compressor. Once inside the compressor, the refrigerant vapor is introduced into a compressor cylinder wherein the vapor is compressed by a piston within the cylinder resulting in an increase in temperature. The vapor exits the cylinder through an exhaust valve, consequently flowing into the discharge portion of the compressor to circulate through the external refrigerant system to return to the compressor unit.
Present practice requires that the design of compressors be as compact as possible, thus the limited available space within the compressor assembly imposes severe size constraints for the suction assembly as well as the discharge elements. Because of this, it is necessary to extend the internal suction system elements, e.g. mufflers, conduits, cavities, in close proximity to other compressor parts that generate and transmit heat.
In the design of high efficiency compressors it is also important to reduce or eliminate noise generated by the suction process. In this regard, some hermetic motor compressors employ a shroud over the open end of the motor assembly to attenuate suction noise generated by pressure pulsations produced by the compressor.
In addition, it is necessary to limit or eliminate the transfer of heat from hot compressor parts such as the wall of the housing, the discharge system, the cylinder block, and the oil, to the relatively cooler intake gas. The intake gas must remain cool to facilitate compressor operation, as overheated intake gas causes an increase in compressor work due to the lowering of the specific gravity of the intake gas reducing the amount of gas entering the cylinder chamber.
Various provisions have been made by the prior art to rectify these problems, such as an intake pipe for the motor compressor being directly connected to a suction muffler of a cylinder head, and within the sealed housing, the intake opening of the suction muffler or suction conduit being disposed as opposed to the tip end of the intake pipe at a minimum distance, or a muffler shell and conduit being formed from a plastic material of low thermal conductivity to minimize heat transfer to the suction gas. Bypass suction conduits, often equipped with the suction mufflers, have also been provided to give continuous unrestricted fluid passageway for suction gas from the motor shroud or from the intake pipe to the suction cavities in the cylinder head.
Commonly, compressor cylinder heads for handling the gas flow for both the discharge and suction sides are manufactured from cast iron or aluminum to provided side-by-side or adjacent suction and discharge cavities separated by dividing walls which were preferably made as thin as possible to allow a maximum suction and discharge plenum volume in the limited amount of available space. In addition, some efforts to overcome the overheating of the suction gas in the cylinder head suction plenum have resulted in tubular liners fabricated from a low thermal conductivity plastic preventing heat transfer to the suction gas, eliminating the suction plenum in the cylinder head and attaching a suction conduit to the relatively thin valve plate, or manufacturing the suction muffler out of a low thermal conductivity plastic. Further arrangements have included utilizing separate discharge and suction cylinder heads for the discharge and suction chambers while the suction cylinder head is formed of a plastic material of low thermal conductivity to minimize heat transfer between the suction and discharge cylinder heads.
However, even with these modifications, the compressors in the prior art are often not acceptable because of various disadvantages such that the transmission of vibration from the compressor to the external piping was increased and that prevention of overheating of the suction ga in the suction cavities of the cylinder head was not sufficient. In addition, these modifications have increased restrictions on the flow of suction gas at the suction port because of the reduced cross-sectional area or the lack of an immediately adjacent suction plenum, also consequently increasing the noise level.
For larger refrigeration and air conditioning single and multi cylinder compressors, such modifications are often not acceptable because of certain disadvantages such as complexity, dimensions of the suction system and discharge system with larger contact areas for the materials with different coefficients of expansion due to heat, limited space, higher oscillation forces of the suction system element due to pressure pulsations, difficulties on assembly, and higher costs.